Biotic FactorsBiotic Factors

Science 10Science 10

Biotic factorsBiotic factors Are factors that affect the Are factors that affect the livingliving environment environment

and include all other organisms that interact and include all other organisms that interact with the individual (either the same species with the individual (either the same species and/or other species). and/or other species). There are There are 55 biotic factors: biotic factors:

1.1. DetritusDetritus: decomposing animals and plants: decomposing animals and plants2.2. DiseaseDisease3.3. Predator/prey interactionsPredator/prey interactions4.4. CompetitionCompetition5.5. Symbiotic relationships Symbiotic relationships (symbiosis).(symbiosis).

1. Detritus1. Detritus Refers to non-living Refers to non-living

organic material such as organic material such as decomposingdecomposing dead dead organisms as well as organisms as well as their wastes. their wastes.

Example:Example:Sea Foam is caused by Sea Foam is caused by decaying organic decaying organic material in the ocean, material in the ocean, such as the dissolved such as the dissolved waste of algal blooms. waste of algal blooms. Organic pollution from Organic pollution from run off water can also run off water can also increase foam increase foam production.  production. 

Detritivores or SaprobesDetritivores or Saprobes Obtain nutrients by consuming Obtain nutrients by consuming

detritus (decomposing organic detritus (decomposing organic matter).matter).Examples:Examples:millipedes, woodlice, terrestrial millipedes, woodlice, terrestrial worms, burying beetlesworms, burying beetles

Micro-organisms such asMicro-organisms such as bacteria, fungi, bacteria, fungi, andand protists protists are are important to an ecosystem important to an ecosystem because they recycle materials because they recycle materials by by “breaking” “breaking” them down into them down into theirtheir “elements” “elements” and returning and returning them to the soil (so plants can them to the soil (so plants can use these nutrients).use these nutrients).

2. Disease2. Disease is the result of an is the result of an

infection by fungi, infection by fungi, bacteria, virus, and other bacteria, virus, and other pathogens. pathogens.

PathogenPathogen::an an infectiousinfectious agent, or agent, or more commonly “more commonly “germgerm”, ”, is a biological agent that is a biological agent that causes disease or illness causes disease or illness to its host.to its host.

Disease is an important Disease is an important biotic factor because biotic factor because disease tends to disease tends to reducereduce the number of organisms the number of organisms within the community. within the community.

3. Predator-Prey Interaction 3. Predator-Prey Interaction (Predation) (Predation)

is another important biotic factor which helps to is another important biotic factor which helps to limitlimit the size of populations within an ecosystem. the size of populations within an ecosystem.

PredationPredation occurs when one animal (the occurs when one animal (the predatorpredator) eats ) eats another living animal (the another living animal (the preyprey) to utilize (or use) the ) to utilize (or use) the energy and nutrients from the body of the prey for its energy and nutrients from the body of the prey for its own growth, maintenance, or reproduction. own growth, maintenance, or reproduction.

Example of PredationExample of PredationJaguar and Tapir Jaguar and Tapir (Belize)(Belize)

When a jaguar kills a When a jaguar kills a tapir for food, the jaguar tapir for food, the jaguar helps to prevent the helps to prevent the overpopulation of the overpopulation of the tapir. tapir.

If the number of tapir If the number of tapir declines too much the declines too much the jaguar will starve. jaguar will starve.

there is a balance there is a balance between the numbers of between the numbers of predator and prey in any predator and prey in any ecosystem. ecosystem.

4. Competition4. Competition IIs a struggle for survival that occurs (or s a struggle for survival that occurs (or

happens) between organisms either of happens) between organisms either of the the samesame or or differentdifferent species. species.

Competition tends to limit the Competition tends to limit the sizesize of the of the population keeping it in population keeping it in balancebalance with the with the available resources. available resources.

2 Types of Competition2 Types of Competition

1.1. Inter-Specific CompetitionInter-Specific Competition: competition : competition between different species.between different species.

ExampleExample:: Lion and hyena or bear and wolf Lion and hyena or bear and wolf competing for foodcompeting for food

2.2. Intra-Specific CompetitionIntra-Specific Competition: competition : competition between species.between species.

ExampleExample: Tigers competing for mates or : Tigers competing for mates or birds competing for nesting space.birds competing for nesting space.

5. Symbiotic 5. Symbiotic RelationshipsRelationships

Are biotic relationships in which different Are biotic relationships in which different organisms live in close association with each organisms live in close association with each other to the other to the benefitbenefit of at least one. of at least one.

There are There are 55 types of symbiotic relationships types of symbiotic relationships including: including:

1.1. MutualismMutualism

2.2. CommensalismCommensalism

3.3. ParasitismParasitism

4.4. ParisitoidismParisitoidism

5.5. Predation. Predation.

Mutualism Mutualism resulting in resulting in mutualmutual benefit benefit

to both of the organisms in to both of the organisms in the relationship. the relationship.

An An example example of this would be of this would be the relationship between the the relationship between the algae and fungus of lichens. algae and fungus of lichens.

The fungi penetrate the The fungi penetrate the roots of the plants and roots of the plants and makes soil nitrogen makes soil nitrogen available to the plant, available to the plant, receiving carbohydrates in receiving carbohydrates in return. This allows them to return. This allows them to live in an environment in live in an environment in which neither could survive which neither could survive alone. alone.

An An exampleexample is a is a polyp found in the polyp found in the deep water off the deep water off the coast of coast of NewfoundlandNewfoundland

It attaches itself to It attaches itself to the shell of a certain the shell of a certain species of the hermit species of the hermit crab, and by crab, and by budding, covers the budding, covers the entire shell with a entire shell with a colony that dissolves colony that dissolves the original shell.the original shell.

Because the colony Because the colony grows at the same rate grows at the same rate as the crab, it provides as the crab, it provides continuous protection, continuous protection, and the crab does not and the crab does not shed its shell at periodic shed its shell at periodic (varying) intervals as it (varying) intervals as it normally would.normally would.

The polyp in turn The polyp in turn benefits by moving benefits by moving around with the crab around with the crab (mobile) thus obtaining a (mobile) thus obtaining a greater food supply then greater food supply then it would obtain if it would obtain if attached to a stationary attached to a stationary object (immobile). object (immobile).

Commensalism Commensalism

relationship in which one organism relationship in which one organism benefits from the relationship but the benefits from the relationship but the other organism seems to other organism seems to neitherneither be be harmedharmed nor nor benefitsbenefits. .

An example of An example of commensalismcommensalism is is the relationship the relationship between trees and between trees and nesting birds. nesting birds.

The tree provides a The tree provides a nesting space for the nesting space for the bird but the bird may bird but the bird may neither harm nor neither harm nor benefit the tree. benefit the tree.

On the other hand, if the bird eats insects On the other hand, if the bird eats insects that normally cause harm to the tree or if that normally cause harm to the tree or if the bird produces wastes that are the bird produces wastes that are absorbed by the tree, one might argue absorbed by the tree, one might argue that the tree and the bird both benefit. that the tree and the bird both benefit.

In this case the example would be In this case the example would be considered considered mutualismmutualism. .

It is often difficult to determine the It is often difficult to determine the complete nature of any relationship and complete nature of any relationship and as a result it is often difficult to distinguish as a result it is often difficult to distinguish between mutualism and between mutualism and commensalismcommensalism. .

The anemonefish lives The anemonefish lives among the forest of among the forest of tentacles of an tentacles of an anemone and is anemone and is protected from protected from potential predators not potential predators not immune to the sting of immune to the sting of the anemone. the anemone.

The anemonefish is The anemonefish is protected from the protected from the sting of the anomone sting of the anomone tentacles by a tentacles by a substance contained in substance contained in the mucous on its skin. the mucous on its skin.

The anemone treats The anemone treats the fish as part of itself the fish as part of itself and does not sting it.and does not sting it.

Parasitism Parasitism

is a symbiotic relationship in which one is a symbiotic relationship in which one organism benefits and the other is harmed. organism benefits and the other is harmed.

The organism that benefits is called the The organism that benefits is called the parasiteparasite, the organism that is harmed is called , the organism that is harmed is called the the hosthost. .

Some parasites only cause slight damage to Some parasites only cause slight damage to their host, while others kill them. their host, while others kill them.

An example would be the tapeworm. They live An example would be the tapeworm. They live in the digestive tracts of various organisms, in the digestive tracts of various organisms, while there they are provided with nutrients and while there they are provided with nutrients and an environment in which to grow and an environment in which to grow and reproduce. reproduce.

However, the host is harmed by the presence However, the host is harmed by the presence of the tapeworm. of the tapeworm.

Parisitoidism Parisitoidism

similar to parasitism. One organism similar to parasitism. One organism benefits but the other is benefits but the other is eventually killedeventually killed - a sort of slow death. - a sort of slow death.

An example is when An example is when a female wasp stings a female wasp stings a spider causing a spider causing paralysis but not paralysis but not death. death.

The wasp then lays a The wasp then lays a single egg on the single egg on the spider. spider.

When the egg When the egg hatches into a larva, hatches into a larva, it slowly eats the it slowly eats the body of the spider body of the spider eventually killing it - eventually killing it - but slowly. but slowly.

Predation Predation

is where the interaction is beneficial to is where the interaction is beneficial to one species and detrimental to the other.one species and detrimental to the other.

This is not always considered a symbiotic This is not always considered a symbiotic relationship, although it is quite similar to relationship, although it is quite similar to parasitism, except for the degree of harm parasitism, except for the degree of harm to the host or prey. to the host or prey.

With predation, the prey is killed. With predation, the prey is killed.

An example An example of predation of predation is when a lion is when a lion kills an kills an antelope and antelope and eats it as its eats it as its source of source of foodfood. .